// Copyright (c) 2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <node/chainstate.h>

#include <chainparams.h>
#include <config.h>
#include <consensus/params.h>
#include <kernel/caches.h>
#include <node/blockstorage.h>
#include <util/fs.h>
#include <validation.h>

using kernel::CacheSizes;

namespace node {
// Complete initialization of chainstates after the initial call has been made
// to ChainstateManager::InitializeChainstate().
static ChainstateLoadResult CompleteChainstateInitialization(
    ChainstateManager &chainman, const CacheSizes &cache_sizes,
    const ChainstateLoadOptions &options) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
    auto &pblocktree{chainman.m_blockman.m_block_tree_db};
    // new CBlockTreeDB tries to delete the existing file, which
    // fails if it's still open from the previous loop. Close it first:
    pblocktree.reset();
    pblocktree = std::make_unique<CBlockTreeDB>(
        DBParams{.path = chainman.m_options.datadir / "blocks" / "index",
                 .cache_bytes = cache_sizes.block_tree_db,
                 .memory_only = options.block_tree_db_in_memory,
                 .wipe_data = options.reindex,
                 .options = chainman.m_options.block_tree_db});

    if (options.reindex) {
        pblocktree->WriteReindexing(true);
        // If we're reindexing in prune mode, wipe away unusable block
        // files and all undo data files
        if (options.prune) {
            chainman.m_blockman.CleanupBlockRevFiles();
        }
    }

    // If necessary, upgrade from older database format.
    // This is a no-op if we cleared the block tree db with -reindex
    // or -reindex-chainstate
    if (!pblocktree->Upgrade()) {
        return {ChainstateLoadStatus::FAILURE,
                _("Error upgrading block index database")};
    }

    if (options.check_interrupt && options.check_interrupt()) {
        return {ChainstateLoadStatus::INTERRUPTED, {}};
    }

    // LoadBlockIndex will load m_have_pruned if we've ever removed a
    // block file from disk.
    // Note that it also sets fReindex global based on the disk flag!
    // From here on, fReindex and options.reindex values may be different!
    if (!chainman.LoadBlockIndex()) {
        if (options.check_interrupt && options.check_interrupt()) {
            return {ChainstateLoadStatus::INTERRUPTED, {}};
        }

        return {ChainstateLoadStatus::FAILURE,
                _("Error loading block database")};
    }

    if (!chainman.BlockIndex().empty() &&
        !chainman.m_blockman.LookupBlockIndex(
            chainman.GetConsensus().hashGenesisBlock)) {
        // If the loaded chain has a wrong genesis, bail out immediately
        // (we're likely using a testnet datadir, or the other way around).
        return {ChainstateLoadStatus::FAILURE_INCOMPATIBLE_DB,
                _("Incorrect or no genesis block found. Wrong datadir for "
                  "network?")};
    }

    // Check for changed -prune state.  What we are concerned about is a
    // user who has pruned blocks in the past, but is now trying to run
    // unpruned.
    if (chainman.m_blockman.m_have_pruned && !options.prune) {
        return {
            ChainstateLoadStatus::FAILURE,
            _("You need to rebuild the database using -reindex to go back to "
              "unpruned mode.  This will redownload the entire blockchain")};
    }

    // At this point blocktree args are consistent with what's on disk.
    // If we're not mid-reindex (based on disk + args), add a genesis
    // block on disk (otherwise we use the one already on disk). This is
    // called again in ImportBlocks after the reindex completes.
    if (!fReindex && !chainman.ActiveChainstate().LoadGenesisBlock()) {
        return {ChainstateLoadStatus::FAILURE,
                _("Error initializing block database")};
    }

    auto is_coinsview_empty =
        [&](Chainstate *chainstate) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
            return options.reindex || options.reindex_chainstate ||
                   chainstate->CoinsTip().GetBestBlock().IsNull();
        };

    assert(chainman.m_total_coinstip_cache > 0);
    assert(chainman.m_total_coinsdb_cache > 0);

    // Conservative value which is arbitrarily chosen, as it will ultimately be
    // changed by a call to `chainman.MaybeRebalanceCaches()`. We just need to
    // make sure that the sum of the two caches (40%) does not exceed the
    // allowable amount during this temporary initialization state.
    double init_cache_fraction = 0.2;

    // At this point we're either in reindex or we've loaded a useful
    // block tree into BlockIndex()!

    for (Chainstate *chainstate : chainman.GetAll()) {
        LogPrintf("Initializing chainstate %s\n", chainstate->ToString());

        chainstate->InitCoinsDB(
            /* cache_size_bytes */ chainman.m_total_coinsdb_cache *
                init_cache_fraction,
            /* in_memory */ options.coins_db_in_memory,
            /* should_wipe */ options.reindex || options.reindex_chainstate);

        if (options.coins_error_cb) {
            chainstate->CoinsErrorCatcher().AddReadErrCallback(
                options.coins_error_cb);
        }

        // Refuse to load unsupported database format.
        // This is a no-op if we cleared the coinsviewdb with -reindex
        // or -reindex-chainstate
        if (chainstate->CoinsDB().NeedsUpgrade()) {
            return {ChainstateLoadStatus::FAILURE_INCOMPATIBLE_DB,
                    _("Unsupported chainstate database format found. "
                      "Please restart with -reindex-chainstate. This will "
                      "rebuild the chainstate database.")};
        }

        // ReplayBlocks is a no-op if we cleared the coinsviewdb with
        // -reindex or -reindex-chainstate
        if (!chainstate->ReplayBlocks()) {
            return {ChainstateLoadStatus::FAILURE,
                    _("Unable to replay blocks. You will need to rebuild the "
                      "database using -reindex-chainstate.")};
        }

        // The on-disk coinsdb is now in a good state, create the cache
        chainstate->InitCoinsCache(chainman.m_total_coinstip_cache *
                                   init_cache_fraction);
        assert(chainstate->CanFlushToDisk());

        if (!is_coinsview_empty(chainstate)) {
            // LoadChainTip initializes the chain based on CoinsTip()'s
            // best block
            if (!chainstate->LoadChainTip()) {
                return {ChainstateLoadStatus::FAILURE,
                        _("Error initializing block database")};
            }
            assert(chainstate->m_chain.Tip() != nullptr);
        }
    }

    // Now that chainstates are loaded and we're able to flush to
    // disk, rebalance the coins caches to desired levels based
    // on the condition of each chainstate.
    chainman.MaybeRebalanceCaches();

    return {ChainstateLoadStatus::SUCCESS, {}};
}

ChainstateLoadResult LoadChainstate(ChainstateManager &chainman,
                                    const CacheSizes &cache_sizes,
                                    const ChainstateLoadOptions &options) {
    if (!chainman.AssumedValidBlock().IsNull()) {
        LogPrintf("Assuming ancestors of block %s have valid signatures.\n",
                  chainman.AssumedValidBlock().GetHex());
    } else {
        LogPrintf("Validating signatures for all blocks.\n");
    }
    LogPrintf("Setting nMinimumChainWork=%s\n",
              chainman.MinimumChainWork().GetHex());
    if (chainman.MinimumChainWork() <
        UintToArith256(chainman.GetConsensus().nMinimumChainWork)) {
        LogPrintf("Warning: nMinimumChainWork set below default value of %s\n",
                  chainman.GetConsensus().nMinimumChainWork.GetHex());
    }
    if (chainman.m_blockman.GetPruneTarget() ==
        BlockManager::PRUNE_TARGET_MANUAL) {
        LogPrintf(
            "Block pruning enabled.  Use RPC call pruneblockchain(height) to "
            "manually prune block and undo files.\n");
    } else if (chainman.m_blockman.GetPruneTarget()) {
        LogPrintf("Prune configured to target %u MiB on disk for block and "
                  "undo files.\n",
                  chainman.m_blockman.GetPruneTarget() / 1024 / 1024);
    }

    LOCK(cs_main);
    chainman.m_total_coinstip_cache = cache_sizes.coins;
    chainman.m_total_coinsdb_cache = cache_sizes.coins_db;

    // Load the fully validated chainstate.
    chainman.InitializeChainstate(options.mempool);

    // Load a chain created from a UTXO snapshot, if any exist.
    bool has_snapshot = chainman.DetectSnapshotChainstate(options.mempool);

    if (has_snapshot && (options.reindex || options.reindex_chainstate)) {
        LogPrintf(
            "[snapshot] deleting snapshot chainstate due to reindexing\n");
        if (!chainman.DeleteSnapshotChainstate()) {
            return {ChainstateLoadStatus::FAILURE_FATAL,
                    Untranslated("Couldn't remove snapshot chainstate.")};
        }
    }

    {
        auto [init_status, init_error] =
            CompleteChainstateInitialization(chainman, cache_sizes, options);
        if (init_status != ChainstateLoadStatus::SUCCESS) {
            return {init_status, init_error};
        }
    }

    // If a snapshot chainstate was fully validated by a background chainstate
    // during the last run, detect it here and clean up the now-unneeded
    // background chainstate.
    //
    // Why is this cleanup done here (on subsequent restart) and not just when
    // the snapshot is actually validated? Because this entails unusual
    // filesystem operations to move leveldb data directories around, and that
    // seems too risky to do in the middle of normal runtime.
    auto snapshot_completion = chainman.MaybeCompleteSnapshotValidation();

    if (snapshot_completion == SnapshotCompletionResult::SKIPPED) {
        // do nothing; expected case
    } else if (snapshot_completion == SnapshotCompletionResult::SUCCESS) {
        LogPrintf("[snapshot] cleaning up unneeded background chainstate, then "
                  "reinitializing\n");
        if (!chainman.ValidatedSnapshotCleanup()) {
            return {ChainstateLoadStatus::FAILURE_FATAL,
                    Untranslated(
                        "Background chainstate cleanup failed unexpectedly.")};
        }

        // Because ValidatedSnapshotCleanup() has torn down chainstates with
        // ChainstateManager::ResetChainstates(), reinitialize them here without
        // duplicating the blockindex work above.
        assert(chainman.GetAll().empty());
        assert(!chainman.IsSnapshotActive());
        assert(!chainman.IsSnapshotValidated());

        chainman.InitializeChainstate(options.mempool);

        // A reload of the block index is required to recompute
        // setBlockIndexCandidates for the fully validated chainstate.
        chainman.ActiveChainstate().ClearBlockIndexCandidates();

        auto [init_status, init_error] =
            CompleteChainstateInitialization(chainman, cache_sizes, options);
        if (init_status != ChainstateLoadStatus::SUCCESS) {
            return {init_status, init_error};
        }
    } else {
        return {ChainstateLoadStatus::FAILURE,
                _("UTXO snapshot failed to validate. "
                  "Restart to resume normal initial block download, or try "
                  "loading a different snapshot.")};
    }

    return {ChainstateLoadStatus::SUCCESS, {}};
}

ChainstateLoadResult
VerifyLoadedChainstate(ChainstateManager &chainman,
                       const ChainstateLoadOptions &options) {
    auto is_coinsview_empty =
        [&](Chainstate *chainstate) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
            return options.reindex || options.reindex_chainstate ||
                   chainstate->CoinsTip().GetBestBlock().IsNull();
        };

    LOCK(cs_main);

    for (Chainstate *chainstate : chainman.GetAll()) {
        if (!is_coinsview_empty(chainstate)) {
            const CBlockIndex *tip = chainstate->m_chain.Tip();
            if (tip && tip->nTime > GetTime() + MAX_FUTURE_BLOCK_TIME) {
                return {ChainstateLoadStatus::FAILURE,
                        _("The block database contains a block which appears "
                          "to be from the future. "
                          "This may be due to your computer's date and time "
                          "being set incorrectly. "
                          "Only rebuild the block database if you are sure "
                          "that your computer's date and time are correct")};
            }

            VerifyDBResult result =
                CVerifyDB(chainman.GetNotifications())
                    .VerifyDB(*chainstate, chainstate->CoinsDB(),
                              options.check_level, options.check_blocks);
            switch (result) {
                case VerifyDBResult::SUCCESS:
                case VerifyDBResult::SKIPPED_MISSING_BLOCKS:
                    break;
                case VerifyDBResult::INTERRUPTED:
                    return {ChainstateLoadStatus::INTERRUPTED,
                            _("Block verification was interrupted")};
                case VerifyDBResult::CORRUPTED_BLOCK_DB:
                    return {ChainstateLoadStatus::FAILURE,
                            _("Corrupted block database detected")};
                case VerifyDBResult::SKIPPED_L3_CHECKS:
                    if (options.require_full_verification) {
                        return {
                            ChainstateLoadStatus::FAILURE_INSUFFICIENT_DBCACHE,
                            _("Insufficient dbcache for block verification")};
                    }
                    break;
            } // no default case, so the compiler can warn about missing cases
        }
    }

    return {ChainstateLoadStatus::SUCCESS, {}};
}
} // namespace node
